The present invention relates to content distribution systems equipped with a terminal device having a storage section storing video, audio, or the like, and a distribution device transmitting content to the terminal device.
In a content distribution system that distributes contents, such as digital video and digital audio compressed according to MPEG, to terminal devices by utilizing a digital broadcasting system and a high-speed network, terminal devices can receive and reproduce the distributed contents and can store in storing devices connected to the terminal devices, such as DVDs or hard disks. The contents stored in the storing devices that are provided for the terminal devices can be reproduced at different times for the respective terminal devices.
FIG. 10 shows the configuration of a conventional content distribution system 9. The content distribution system 9 has a distribution device 97 and a plurality of terminal devices 95 that are connected to each other by a distribution network 2 and a management network 3. The distribution device 97 has a content-storing section 93 in which contents are stored, and it distributes the contents stored in the content-storing section 93 to the plurality of terminal device 95 through the distribution network 2. The distributed contents are stored in the storing section 98 provided in each of the terminal devices.
In the content distribution system 9 having such a configuration, as the distribution device 97 reads out a content stored in the content-storing section 93 and distributes it to the plurality of terminal device 95 through the distribution network 2, each of the terminal devices 95 receives and reproduces the distributed content. Each of the terminal devices 95 stores the received content into the storing section 98, and it reproduces the content stored in the storing section 98 at a date and hour different from the date and hour at which the contents are received.
When a desired content is neither being distributed from the distribution device 97 nor stored in the storing section 98 provided in the terminal device 95, the terminal device 95 requests the distribution device 97 to send the desired content through the management network 3. The distribution device 97 reads out the requested content from the content-storing section 93, and transmits the content to the terminal device 95 that has made the request through the distribution network 2. The terminal device 95 that has received the requested content reproduces the content and/or stores it into the storing section 98.
When a plurality of terminal devices 95 request the distribution device 97 to send different contents, it is possible that there will be a shortage of transfer band of the distribution network 2 that is used to distribute the different contents to each of the terminal devices 95. Especially, when video or audio contents compressed according to the MPEG standard are attempted to distribute, the distribution device 97 is required to have an extremely large transmission capability because such contents have a very large file size. For example, when different 5 Mbps video data of MPEG-2 MP@ML are attempted to distribute to 10 terminal devices 95, the distribution device 97 needs to transmit video data of about 50 Mbits per 1 second.
As a solution to this problem, the following techniques (1) to (4) have been known.
(1) The transmission capability of the distribution device 97 is increased.
(2) The number of terminal devices 95 is restricted according to the transmission capability of the distribution device 97.
(3) An upper limit is set for the data amount of the content to be distributed by the distribution device 97.
(4) The contents that a terminal device 95 can request are restricted to those with a small file size.
When the transmission capability of the distribution device 97 is increased according to the technique (1) above, the scale of the distribution device 97 becomes very large. In addition, at least one of the above techniques (2) through (4) must be employed at the same time because an upper limit must be set for the transmission capability of the distribution device 97, although the scale of the distribution device 97 becomes very large.
In the above technique (2), the number of terminal devices 95 is restricted, and for this reason, if contents are to be distributed to a greater number of terminal devices than the restricted number, it is necessary to provide two or more of the content distribution systems 9 shown in FIG. 10.
In the above technique (3), the data amount of contents has an upper limit, and therefore, high quality video or audio having a larger data amount than the set upper limit of data amount cannot be distributed.
In the above technique (4), the content that a terminal device 95 can request is restricted to, for example, a content having a small file size.